1. Field of the Invention
The present invention relates to temperature compensating ceramic dielectrics. More particularly, it relates to ceramic dielectrics for temperature-compensating ceramic capacitors with a temperature coefficient of permittivity ranging from +30.times.10.sup.-6 to -300.times.10.sup.-6 /.degree.C., high permittivity and high Q at high frequencies, that can be sintered at a relatively low temperature.
2. Description of the Prior Art
As a ceramic dielectric material for temperature-compensating ceramic capacitors, there have been known ceramic dielectrics mainly comprising neodymium oxide (Nd.sub.2 O.sub.3), barium oxide (BaO) and titanium oxide (TiO.sub.2), and containing a minor quantity of bismuth oxide (Bi.sub.2 O.sub.3) or lead oxide (PbO or Pb.sub.3 O.sub.4) incorporated therein. However, compositions of such dielectric materials have a high sintering temperature ranging from 1270.degree. to 1400.degree. C., resulting in the increase of manufacturing cost of capacitors. For example, multi-layer ceramic capacitors are generally produced by a process comprising the steps of preparing ceramic green sheets, forming an internal electrode on each ceramic green sheet, placing the resultant ceramic green sheets one over another, and firing the resultant multi-layered body. In such a process, baking of the internal electrodes is carried out simultaneously with the sintering of the ceramic material, so that a material for the internal electrodes is required to have a high melting point over the firing temperature of 1270.degree. to 1400.degree. C. It is therefore required to use a high-melting point, noble metal such as Pt, Au, Pd, etc., resulting in the increase of the cost of the multi-layer ceramic capacitors.